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Liquid water that falls from the atmosphere to the earth. Temperatures below 0C cause the rain to become sleet or snow. When the liquid drops are suspended in the atmosphere as clouds, they may absorb components from the air such as Carbon dioxide or pollutants. Carbon dioxide will form carbonic acid and decrease the pH of rain as low as 5.6. Acid rain occurs when pH levels are below this point due to the presence of other types of pollutants, such as Sulfur dioxide.

Synonyms and Related Terms

precipitation; chuva (Port.)

Physical and Chemical Properties

Diameter of drops = greater than 0.5 mm (0.02 inch) but smaller than 4 mm

Resources and Citations

  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997